The cap forbids local governments from hiking property tax rates by more than 2% annually or by the cost of inflation — whichever is lowest. In Albany, it is anticipated that the cap will be set at 2% this year just as it was the year before.

The cap was adopted last year, and district officials from several Southern Tier school districts said that it has severely limited their ability to raise needed funds, forcing them to make staff cuts and layoffs. The union is arguing that the requirement that 60% of voters must agree before the cap could be set aside creates funding inequality, since they contend that wealthier districts will have an easier time passing the override than poorer ones.

“As we look at the impact of both the cuts in state aid and the property-tax cap, the reality is that the wealth gap and the ability of poorer school districts to provide a sound basic education, whatever that means today, is much more difficult than it has been in the past — and much more difficult than it is for wealthier districts,” Iannuzzi said. “So, just on its face, what’s the reason for that? And is it the property tax cap, and is it the way we fund education?

Iannuzzi anticipates that the lawsuit will be filed sometime before the end of this year.

Governor Andrew Cuomo threw his support behind the cap which he saw as a key tool for bringing the state’s property tax rates — some of the highest in the country — into line. In a report released last week, he said that the cap did its job by keeping the tax rate growth at 2% in 92% of the state’s school districts.

“Governor Cuomo’s tax cap has been an unqualified success that, as was reported yesterday, has kept property tax increases 40 percent lower than the average of the last 10 years,” said Richard Azzopardi, a Cuomo spokesman.

“Taxpayers simply can’t afford to go back to the bad old days and have New York continue to spend more money per student than any other state, while ranking 39th in high school graduation rates.”